The present invention relates to an oscillometric blood pressure measurement apparatus, taking in pressure pulses from a signal corresponding to a pressure of a cuff and calculating a blood pressure based on this signal.
With this type of blood pressure measurement apparatus, a cuff is wound around an upper arm of a subject, pressure pulses are taken in continuously from a signal corresponding to a cuff pressure in a state where the cuff pressure is maintained at a prescribed value, and, when two pressure pulses of a substantially same waveform occurs continuously, recognizing the pressure pulses as pressure pulses that can be used for blood pressure calculation, and thereafter decreasing the cuff pressure in micro steps and measuring pressure pulses in likewise manner. These measurements are performed until calculation of the blood pressure is enabled. Here, there is a problem when arrhythmia occurs and an amplitude of a pressure pulse and a pulse rate change due to an extrasystole, etc. In this case, two continuous pressure pulses are not acquired and because measurements are made repeatedly while maintaining the cuff pressure until the pulses are acquired, much time is required for measurement. These circumstances are described, for example, in paragraph 0006 and FIG. 2 in JP-A-2002-112972.
To solve the above issue, in JP-A-2002-112972, a sensor (ECG sensor), detecting presence of arrhythmia, is used, detection is performed using a first pulsation complex criterion when arrhythmia is not detected, and detection is performed using a second pulsation complex criterion that is more lax than the first pulsation complex criterion to compensate for presence of arrhythmia when arrhythmia is detected.
In JP-A-2003-144399, by a cuff pulse wave amplitude correcting unit, correcting a cuff pulse wave amplitude, an amplitude of each cuff pulse wave is corrected based on a nonlinear relationship between a pressure difference, which is a difference between a cuff pressure and a mean blood pressure of a living body, and the cuff pulse wave amplitude, and because a blood pressure value of the living body is determined based on a change of the corrected cuff pulse wave amplitude, even when arrhythmia occurs, an accurate envelope is determined to enable blood pressure measurement to be performed or blood pressure measurement to be performed at high precision.
The apparatus described in JP-A-2002-112972 requires a sensor specialized to detect the presence of arrhythmia and this leads to making the configuration complex and large. The apparatus described in JP-A-2003-144399 requires a photoplethysmograph as the cuff pulse wave amplitude correcting unit and this also leads to making the configuration complex and large.